//===- ConstraintManager.h - Constraints on symbolic values. ----*- C++ -*-===//

//

// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.

// See https://llvm.org/LICENSE.txt for license information.

// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception

//

//===----------------------------------------------------------------------===//

//

//  This file defined the interface to manage constraints on symbolic values.

//

//===----------------------------------------------------------------------===//

#ifndef LLVM_CLANG_STATICANALYZER_CORE_PATHSENSITIVE_CONSTRAINTMANAGER_H

#define LLVM_CLANG_STATICANALYZER_CORE_PATHSENSITIVE_CONSTRAINTMANAGER_H

#include "clang/Basic/LLVM.h"

#include "clang/StaticAnalyzer/Core/PathSensitive/ProgramState_Fwd.h"

#include "clang/StaticAnalyzer/Core/PathSensitive/SVals.h"

#include "clang/StaticAnalyzer/Core/PathSensitive/SymExpr.h"

#include "llvm/ADT/Optional.h"

#include "llvm/Support/SaveAndRestore.h"

#include <memory>

#include <utility>

namespace llvm {

class APSInt;

} // namespace llvm

namespace clang {

namespace ento {

class ProgramStateManager;

class SubEngine;

class SymbolReaper;

class ConditionTruthVal {

  Optional<bool> Val;

public:

  /// Construct a ConditionTruthVal indicating the constraint is constrained

  /// to either true or false, depending on the boolean value provided.

  ConditionTruthVal(bool constraint) : Val(constraint) {}

  /// Construct a ConstraintVal indicating the constraint is underconstrained.

  ConditionTruthVal() = default;

  /// \return Stored value, assuming that the value is known.

  /// Crashes otherwise.

  bool getValue() const {

    return *Val;

  }

  /// Return true if the constraint is perfectly constrained to 'true'.

  bool isConstrainedTrue() const {

    return Val.hasValue() && 
Val.getValue()36.5k
;

  }

  /// Return true if the constraint is perfectly constrained to 'false'.

  bool isConstrainedFalse() const {

    return Val.hasValue() && 
!Val.getValue()735
;

  }

  /// Return true if the constrained is perfectly constrained.

  bool isConstrained() const {

    return Val.hasValue();

  }

  /// Return true if the constrained is underconstrained and we do not know

  /// if the constraint is true of value.

  bool isUnderconstrained() const {

    return !Val.hasValue();

  }

};

class ConstraintManager {

public:

  ConstraintManager() = default;

  virtual ~ConstraintManager();

  virtual bool haveEqualConstraints(ProgramStateRef S1,

                                    ProgramStateRef S2) const = 0;

  virtual ProgramStateRef assume(ProgramStateRef state,

                                 DefinedSVal Cond,

                                 bool Assumption) = 0;

  using ProgramStatePair = std::pair<ProgramStateRef, ProgramStateRef>;

  /// Returns a pair of states (StTrue, StFalse) where the given condition is

  /// assumed to be true or false, respectively.

  ProgramStatePair assumeDual(ProgramStateRef State, DefinedSVal Cond) {

    ProgramStateRef StTrue = assume(State, Cond, true);

    // If StTrue is infeasible, asserting the falseness of Cond is unnecessary

    // because the existing constraints already establish this.

    if (!StTrue) {

#ifndef __OPTIMIZE__

      // This check is expensive and should be disabled even in Release+Asserts

      // builds.

      // FIXME: __OPTIMIZE__ is a GNU extension that Clang implements but MSVC

      // does not. Is there a good equivalent there?

      assert(assume(State, Cond, false) && "System is over constrained.");

#endif

      return ProgramStatePair((ProgramStateRef)nullptr, State);

    }

    ProgramStateRef StFalse = assume(State, Cond, false);

    if (!StFalse) {

      // We are careful to return the original state, /not/ StTrue,

      // because we want to avoid having callers generate a new node

      // in the ExplodedGraph.

      return ProgramStatePair(State, (ProgramStateRef)nullptr);

    }

    return ProgramStatePair(StTrue, StFalse);

  }

  virtual ProgramStateRef assumeInclusiveRange(ProgramStateRef State,

                                               NonLoc Value,

                                               const llvm::APSInt &From,

                                               const llvm::APSInt &To,

                                               bool InBound) = 0;

  virtual ProgramStatePair assumeInclusiveRangeDual(ProgramStateRef State,

                                                    NonLoc Value,

                                                    const llvm::APSInt &From,

                                                    const llvm::APSInt &To) {

    ProgramStateRef StInRange =

        assumeInclusiveRange(State, Value, From, To, true);

    // If StTrue is infeasible, asserting the falseness of Cond is unnecessary

    // because the existing constraints already establish this.

    if (!StInRange)

      return ProgramStatePair((ProgramStateRef)nullptr, State);

    ProgramStateRef StOutOfRange =

        assumeInclusiveRange(State, Value, From, To, false);

    if (!StOutOfRange) {

      // We are careful to return the original state, /not/ StTrue,

      // because we want to avoid having callers generate a new node

      // in the ExplodedGraph.

      return ProgramStatePair(State, (ProgramStateRef)nullptr);

    }

    return ProgramStatePair(StInRange, StOutOfRange);

  }

  /// If a symbol is perfectly constrained to a constant, attempt

  /// to return the concrete value.

  ///

  /// Note that a ConstraintManager is not obligated to return a concretized

  /// value for a symbol, even if it is perfectly constrained.

  virtual const llvm::APSInt* getSymVal(ProgramStateRef state,

                                        SymbolRef sym) const {

    return nullptr;

  }

  /// Scan all symbols referenced by the constraints. If the symbol is not

  /// alive, remove it.

  virtual ProgramStateRef removeDeadBindings(ProgramStateRef state,

                                                 SymbolReaper& SymReaper) = 0;

  virtual void printJson(raw_ostream &Out, ProgramStateRef State,

                         const char *NL, unsigned int Space,

                         bool IsDot) const = 0;

  /// Convenience method to query the state to see if a symbol is null or

  /// not null, or if neither assumption can be made.

  ConditionTruthVal isNull(ProgramStateRef State, SymbolRef Sym) {

    SaveAndRestore<bool> DisableNotify(NotifyAssumeClients, false);

    return checkNull(State, Sym);

  }

protected:

  /// A flag to indicate that clients should be notified of assumptions.

  /// By default this is the case, but sometimes this needs to be restricted

  /// to avoid infinite recursions within the ConstraintManager.

  ///

  /// Note that this flag allows the ConstraintManager to be re-entrant,

  /// but not thread-safe.

  bool NotifyAssumeClients = true;

  /// canReasonAbout - Not all ConstraintManagers can accurately reason about

  ///  all SVal values.  This method returns true if the ConstraintManager can

  ///  reasonably handle a given SVal value.  This is typically queried by

  ///  ExprEngine to determine if the value should be replaced with a

  ///  conjured symbolic value in order to recover some precision.

  virtual bool canReasonAbout(SVal X) const = 0;

  /// Returns whether or not a symbol is known to be null ("true"), known to be

  /// non-null ("false"), or may be either ("underconstrained").

  virtual ConditionTruthVal checkNull(ProgramStateRef State, SymbolRef Sym);

};

std::unique_ptr<ConstraintManager>

CreateRangeConstraintManager(ProgramStateManager &statemgr,

                             SubEngine *subengine);

std::unique_ptr<ConstraintManager>

CreateZ3ConstraintManager(ProgramStateManager &statemgr, SubEngine *subengine);

} // namespace ento

} // namespace clang

#endif // LLVM_CLANG_STATICANALYZER_CORE_PATHSENSITIVE_CONSTRAINTMANAGER_H